In endoscopic surgery, retractors are used to keep organs away from the operating site, so as to have a clear view and sufficient freedom of movement. The retractors usually have an actuation handle, which is coupled via a shaft to a flexible retraction structure, the latter being composed of several link elements that are interconnected in an articulated manner. For insertion into the body or for passage through a trocar, the link elements are oriented in alignment with the shaft, and it is only when inside the body that they are shaped to form a ring or hook for receiving the organ. In order to be closed to form a ring, the retraction structure has, on the last distal link element, a connecting means connected to the shaft. The ring is shaped with the aid of a second endoscopic instrument, for example gripping forceps, introduced through a further body opening, or by means of a Bowden wire, which is guided in the link elements themselves and which is actuated with the actuation handle. The hinges that connect the individual link elements are designed to be as nontraumatic as possible and can have guide surfaces and/or angled abutments that bring the individual hinges in each case to an optimal angle for closing the ring.
A retractor of the type in question is known from DE 199 20 869 A1 and has a shaft at whose distal end several articulated link elements are arranged that can be adjusted to form a ring, wherein a distal link element can be coupled to the shaft via two locking hooks. The link elements can be brought to the ring position with the aid of a Bowden wire, which is guided within the link elements. The retraction structure can be angled by up to 90° relative to the shaft by a hinge.
In addition to the locking hooks disclosed there, it is also known to arrange a locking pin at the free end of the retraction structure, which locking pin can be brought into releasable engagement with a spring pressure piece in the shaft. Considerable force has to be applied here, both for coupling and also for uncoupling, since the restoring force of the spring pressure piece always has to be overcome; this poses a high risk of injury since an operator can always slip when applying pressure. Moreover, the spring pressure piece can only be cleaned and disinfected with great effort. Proceeding from this prior art, the object of the present invention is to make available an improved retractor for endoscopic surgery, which retractor can be operated more reliably and with application of less force, is easier to clean, and has a high degree of safety as regards operating errors.